1. Field of the Invention
The invention relates to an optical-electrical composite cable having an optical fiber and plural electric wires.
2. Description of the Related Art
A conventional optical-electrical composite cable used for, e.g., signal transmission between electronic devices such as personal computer or display is known in which an optical fiber and plural electric wires are covered all together with a sheath. Some of such optical-electrical composite cables adopt a structure in which an increase in optical loss caused by microbending of the optical fiber (slight bending of a central axis of a core caused by pressure (lateral pressure) applied from a side surface) is suppressed (see, e.g., JP-A-2011-018544 and JP-A-2012-009156).
In the optical-electrical composite cable described in JP-A-2011-018544, an optical fiber is arranged in the center and plural covered conductors are arranged to surround the optical fiber. In addition, a high-tensile fiber such as Kevlar (trademark) is filled between the optical fiber and the plural covered conductors. In this optical-electrical composite cable, an external force from outside of the sheath is absorbed by a covering of the covered conductor and is also dispersed by the high-tensile fiber, and it is thereby possible to reduce lateral pressure acting on the optical fiber.
In the optical-electrical composite cable described in JP-A-2012-009156, an optical fiber is arranged so as to be in contact with an inner peripheral surface of a protective tube and plural electric wires are arranged around an outer periphery of the protective tube. In this optical-electrical composite cable, since the optical fiber is protected from an external force by the protective tube, bending or twisting of the optical fiber due to the external force is suppressed and an increase in transmission loss is thus suppressed.